The leader of the Senate Conservatives Fund emailed supporters on Friday promising to back primary challenges against three Republican incumbents who voted for the Senate immigration bill that passed the chamber Thursday.

"There are three incumbents up next year who supported the amnesty bill," SCF Executive Director Matt Hoskins wrote, calling out Sens. Lindsey Graham of South Carolina, Lamar Alexander or Tennessee, and Susan Collins of Maine. "If strong, conservative challengers emerge in these races, we will support them."

Senate Conservatives Fund is a tea-party aligned group that was founded by former Sen. Jim DeMint. The South Carolina Republican is no longer with the group. Graham, a member of the bipartisan "gang of eight" that drafted the underlying immigration overhaul, indicated in a Thursday Senate floor speech that he knew his position on immigration might create primary problems for him.

"I have never been more proud to be involved in an issue than I have trying to fix illegal immigration because it is a national security threat, it is an economic threat, and it is a cultural threat," Graham said.

"As to my politics, I am doing great among Hispanics in South Carolina. The bad news is that there are not very many who vote in the Republican primary," he added.

Fellow "gang of eight" Republican (and friend of Graham) John McCain of Arizona cautioned the GOP campaign apparatus not to campaign against the immigration measure. Hoskins said Wednesday that if McCain doesn't retire in 2016, he should face a primary challenge. "He's not just a liberal. He's also first class jerk," Hoskins said.

Those comments came in reference to an exchange on the floor between McCain and GOP Sen. Deb Fischer of Nebraska.

"Senator McConnell showed his true colors when he said he hopes the House will pass a bill so a conference committee can negotiate a final deal," Hoskins wrote. "Everyone knows that if this bill is taken behind closed doors they will come up with new fig leaves, add even more earmarks, and twist enough arms to muscle it through the House."

McConnell voted against the bill that passed the Senate. In addition, his requirements for a bill he could support are significantly different than what passed the Senate on Thursday.

Hoskins also expressed displeasure with two senators the group supported in the past: Marco Rubio, R-Fla., and Jeff Flake, R-Ariz. Both voted for the bill.